Study On The Quality And Microbial Diversity Of Passion Fruit Wine By Two Fermentation Methods

In this study,purple passion fruit was used as experimental materials,the physicochemical indices,microbial community composition and the rules of succession,nonvolatile metabolites and volatile flavor substances of passion fruit wine during the fermentation of natural fermentation(NF)and controlled fermentation(CF)were analyzed;the correlations between microorganisms and physicochemical indices,nonvolatile metabolites and volatile flavor substances during the fermentation of passion fruit wine were revealed;by comparing NF and CF,the differences of NF and CF fermentation process were analyzed,and the rules of microbial succession in fermentation process were analyzed;and provided references for understanding the essence of fermentation,revealed the contribution of NF and CF to the characteristic flavor of passion fruit wine and provided a reference for screening functional fermentation strains and optimizing fermentation conditions.The results were as follows:1.The physicochemical indices of passion fruit wine of two fermentation methods showed the same trend,the soluble solids and total sugars decreased and then stabilized,the variation tendency of alcohol content was opposite to it;total acids showed a relatively stable trend after increasing,p H was opposite to it,organic acids showed a dynamic increasing trend;total phenols increased first and then decreased;anthocyanins decreased and then stabilized.The physicochemical indices meets the quality requirements of fruit wine.CF compared to NF,fermentation rate of CF faster than the NF,in addition,the alcohol content and total acids higher than NF and the effect of color protection on fruit wine better than NF.2.The microbial diversity of passion fruit wine during fermentation was analyzed by high-throughput sequencing technology,and the results showed that a total of 8fungal phyla and 135 fungal genera were identified,among which Ascomycota was dominant fungal phylum,while,Debaryomyces,Meyerozyma and Wickerhamomyces were dominant fungal genera;15 bacterial phyla and 130 bacterial genera were identified,in which,Proteobacteria and Firmicutes were dominant bacterial phyla,and Paucibacter,Pantoea,Escherichia＿Shigella,Achromobacter,Lactobacillus and Bifidobacterium were dominant bacterial genera in NF.In CF,a total of 11 fungal phyla and 389 fungal genera were identified,among which,Ascomycota and Basidiomycota were dominant phyla,the dominant fungal genera were Meyerozyma,Cladosporium and Saccharomyces;15 bacterial phyla and 128 bacterial genera were identified,dominant phyla were Proteobacteria and Firmicutes,futhermore,dominant bacterial genera were Paucibacter,Achromobacter and Lactobacillus.The colony structure of different fermentation methods were quite different,which reflected the complexity of the microbial composition in the fermentation process of passion fruit wine.3.Metabolomics technology of gas chromatography-time-of-flight mass spectrometry(GC-TOF-MS)were used to explore the metabolites of passion fruit wine,the results showed that 256 nonvolatile metabolites were identified in 18 samples of passion fruit wine,based on OPLS-DA results,3 key nonvolatile differential metabolites were screened in CF,15 key nonvolatile differential metabolites were screened in NF.The above 18 differential metabolites were annotated to 19 metabolic pathways with significant differences,among which the citrate cycle(TCA cycle)and glyoxylate and dicarboxylate metabolism were the main metabolic pathways.The main nonvolatile metabolites that differ from different fermentation methods were sugars and derivatives(13 types)and organic acids(9 types).4.HS-SPME-GC-MS were used to analyze the flavor substances,128 volatile flavor substances were identified in both CF and NF,including 24 esters,11 alcohols,13 ketones,10 acids,11 alkanes and alkenes,9 benzene rings,3 aldehydes,10 amines,13 kinds of furan,pyrazine and pyridine compounds,and 24 others.Esters played a dominant role in the flavor of passion fruit wine,at the end of fermentation,the content of esters in the CF group(13.85%)was higher than the NF group(11.95%).The volatile flavor types of the CF group were consistent with those of the NF group,and at the end of fermentation,the CF group showed a higher content of flavor substances(except alcohols and aldehydes).5.The correlations between physicochemical indices,metabolites and microorganisms during the fermentation of passion fruit wine were indicated that the variation tendency of Wickerhamomyces was positively correlated with the variation tendency of alcohol content and total acids and negatively correlated with soluble solids and total sugars.The variation tendency of Paucibacter and Pantoea was negatively correlated with the variation tendency of alcohol content and total acids and positively correlated with soluble solids and total sugars.In CF,the variation tendency of Saccharomyces was positively correlated with the variation tendency of alcohol content and total acids and negatively correlated with soluble solids and total sugars.The variation tendency of Paucibacter was positively correlated with the variation tendency of total phenols.In NF,Debaryomyces and Meyerozyma were negatively correlated with 12 nonvolatile differential metabolites;furthermore,there was a significant negative correlation between Pantoea and 3,6-anhydro-D-galactose.In CF,there was a significant positive correlation between Paucibacter and 3 nonvolatile differential metabolites.In NF,Wickerhamomyces,Achromobacter,Bifidobacterium and Lactobacillus were positively correlated with flavor substances such as ethylene glycol acetate formate,2-pentanol,acetate,phenylethyl alcohol,and 1-butanol,3-methyl-et al.In CF,Saccharomyces,Achromobacter and Lactobacillus were positively correlated with a variety of esters and alcohols such as decanoic acid,ethyl ester,dodecanoic acid,ethyl ester,and phenylethyl alcohol.